This 12 residues long fragment (amino acids 3 to14) of the histone 4, is also known as H4-12. Histone acetyltransferase (HAT) p300/CBP catalyzes the acetylation of this N-terminal tail of free histone H4 at Lys5, 8, 12. Lys8 is thought to be the preferred acetylation site in H4. Determinants of interaction of p300 with histone 4 appear to be fully present on H4-12, the N-terminal region of the protein. H4-12. is functionally equal to the longer H4-21 peptide, despite the loss of nine amino acids.